Physics - OCR 21st Century

Physics - OCR 21st Century

1. P1 - The Earth in the Universe

   • The Solar System
     • Planets reflect sunlight and orbit the Sun in Ellipses
       • The Solar System consists of a star (The Sun) and things orbiting it.
         • 8 planets orbiting the Sun in almost circular paths (Ellipses)
         • Closest to the Sun: -Mercury, Venus, Earth and Mars
           • The inner planets
         • The asteroid belt is between the inner and outer planets
         • Furthest from the Sun: -Jupiter, Saturn, Uranus and Neptune
           • The outer planets
       • There are also dwarf planets, comets, dust, etc. that orbit around the Sun.
       • Planets usually having moons orbiting them.
         • They are usually much smaller and found closer to the Sun.
     • Stars and planets are very different from each other
       • Some planets can be seen with the naked eye.
         • They look like stars but are very different.
       • Stars are huge, very hot and very far away. They give out lots of light - which is why you can see them from very far away.
       • Planets are smaller and they just reflect sunlight falling on them.
         • The planets of the Solar System are much closer than the stars.
     • The Solar System is about 5 million years old.
       • 1. Solar System was formed from big clouds of dust and gas.
         • 2. Perhaps from a nearby star exploding, one cloud began to get squeezed tightly.
           • 3. Once particles had moved a bit closer to each other, gravity took over. It pulled things closer and closer together until the whole cloud started to collapse in on itself.
             • 4. At the centre of collapse